The effect of conscious and non-conscious presentation of biologically relevant emotion pictures on emotion modulated startle and phasic heart rate.

Many researchers have proposed an emotion regulation circuit that includes the prefrontal cortex and the amygdala. LeDoux (1996) has proposed that there are two pathways by which emotion information is processed. A fast route that bypasses the prefrontal cortex to allow rapid response to potential threat, and a slower route that includes the prefrontal cortex and allows modulation of bottom-up inputs. We investigated these pathways and their peripheral manifestations using emotional pictures presented for either 30 milliseconds or 6 seconds. 36 female participants were randomly assigned to view pleasant, unpleasant, and neutral pictures that varied in viewing time while the eyeblink startle magnitude and phasic heart rate (HR) responses were recorded. Significant Group by Valence interactions were found for both startle and heart rate responses. For the 6 second condition the expected emotion modulated startle effect was found with a larger startle for unpleasant and smaller startles for pleasant foregrounds relative to neutral pictures. For HR, the D1 component was larger for pleasant and unpleasant foregrounds compared to the neutral and the A1 component was larger for the unpleasant compared to the pleasant and the neutral. For the 30 millisecond condition, startle magnitudes were larger for the pleasant and unpleasant compared to the neutral. Whereas the HR response showed the expected tri-phasic profile there were no significant between valence differences. These results suggest that briefly presented emotion stimuli access the fast route of emotion recognition perhaps via the amygdala. The 6 second presentations allow the prefrontal cortex to modulate the bottom up inputs and thus produce a context appropriate response.